1. Field of the Invention
The present invention relates to improved cementing operations, particularly cementing wells penetrating subterranean formations.
In particular, the present invention relates to additives to cementing compositions employed in cementing operations, for the purpose of reducing fluid loss from the cementing composition to the surrounding environment.
More particularly, the present invention relates to copolymers of hydrolyzed acrylamide and 2-acrylamido-2-methylpropane sulfonic acid derivatives as fluid loss additives to aqueous hydraulic cement slurries and the use of such slurries in cementing operations.
More particularly, the present invention concerns cementing of gas and oil wells employing aqueous hydraulic cement slurries containing copolymers of hydrolyzed acrylamide and 2-acrylamido-2-methylpropane sulfonic acid derivatives which reduce fluid loss from the cement slurry to the surrounding subterranean formation which the well has penetrated.
The term "aqueous hydraulic cement slurry" as employed herein is also intended to include aqueous suspensions or slurries of solids constituting raw materials, precursors, or intermediate materials used in preparation or manufacture of hydraulic cements as hereinafter defined. Thus, the present invention includes reducing the fluid loss of aqueous slurries of materials handled during conventional wet processing of cement. This improves the suspension of solids in the water being used as a vehicle to transport and intermix the solids during wet processing.
2. The Prior Art
Polymer compositions have long been used as additives to cementing compositions for the purpose of reducing water loss. For example, U.S. Pat. No. 2,614,998 discloses the use of water-soluble alkali salts of partially hydrolyzed polyacrylamide and polyacrylic acid for reducing the filtration of water from cement slurries. U.S. Pat. No. 2,865,876 discloses the use of sulfonated polystyrene as a fluid loss reducing additive. Other compositions known in the art to be useful for reducing fluid loss from cementing compositions are, among others, polyvinyl sulfonic acid disclosed in U.S. Pat. No. 2,905,565; the calcium soaps of alkyl sulfonic acids, alkaryl sulfonic acids, and petroleum sulfonic acids, disclosed in U.S. Pat. No. 3,052,628; poly(ar-vinylbenzyl)sulfonium alkyl substituted bases and salts disclosed in U.S. Pat. No. 3,094,501; and sulfonated poly(2,6-dimethylphenol) disclosed in U.S. Pat. No. 3,302,716.